The invention relates to communication terminals, and in particular to terminals having an output device providing human-understandable information.
Previously, terminal devices were allowed to communicate in a communication system after executing precise protocols and the exchange of information allowing those devices expected to be in the communication session to select the proper logic and formats. In this manner, they would be consistent. This exchange of information is known as "handshaking," and once the communication session was established the information was not kept and became lost, except possibly for an error log kept at a host system for the communication system. The "handshaking" procedure, if successful, therefore appeared transparent to the terminal operator because the operator was largely inactive during the procedure. Rather, only the preset logic of each of the machines was involved.
The operator was informed when the session was established, or informed that the session attempt was unsuccessful. If successful, the terminal operator normally proceeded with one or more exchanges employing the terminal, including communication with the communication system over the established session.
Often, only after the operator has completed preparatory work and begins an active session, did the operator learn that the session could not be fruitful because the session or the communication system was not exactly the same as was expected. Examples include: the central processing unit to which the session is established is not the type expected; a desired device of the communication system is not on line; the format required for the established data session is different than that for which the operator has prepared. The operator must then either wait until another time to reestablish the session and conduct his exchange, or redo much of his preparatory work in view of the differing circumstances.